status.words.py: Make Contact a proper IStatusReceiver

Since Contact is an IStatusReceiver, it (and its subclasses) should
declare that they implement IStatusReceiver. As well, make Contact
inherit from base.StatusReceiver so that the unimplemented
IStatusReceiver methods do not need to be stubbed out.

Add a note to developer.texinfo saying that this pattern should[*] be
followed for all IStatusReceivers.

[*] "should" instead of "must" as of 9c2bf24 (make notifications a bit
more resilient to missing methods, 2010-02-13) and c79f09b (check for
notification methods before calling them, 2010-02-15)

buildbot/status/words.py

@@ -13,6 +13,7 @@
 
 from buildbot import interfaces, util
 from buildbot import version
+from buildbot.interfaces import IStatusReceiver
 from buildbot.sourcestamp import SourceStamp
 from buildbot.status import base
 from buildbot.status.builder import SUCCESS, WARNINGS, FAILURE, EXCEPTION
@@ -57,7 +58,8 @@ def started(self, s):
         d = s.waitUntilFinished()
         d.addCallback(self.parent.watchedBuildFinished)
 
-class Contact:
+class Contact(base.StatusReceiver):
+    implements(IStatusReceiver)
     """I hold the state for a single user's interaction with the buildbot.
 
     This base class provides all the basic behavior (the queries and
@@ -70,6 +72,7 @@ class Contact:
     """
 
     def __init__(self, channel):
+        #StatusReceiver.__init__(self) doesn't exist
         self.channel = channel
         self.notify_events = {}
         self.subscribed = 0
@@ -284,10 +287,6 @@ def requestSubmitted(self, brstatus):
         log.msg('[Contact] BuildRequest for %s submitted to Builder %s' %
             (brstatus.getSourceStamp(), brstatus.builderName))
 
-    def requestCancelled(self, brstatus):
-        # nothing happens with this notification right now
-        pass
-
     def builderRemoved(self, builderName):
         log.msg('[Contact] Builder %s removed' % (builderName))
 
@@ -348,15 +347,6 @@ def buildFinished(self, builderName, build, results):
 
         self.send(r)
 
-    def changeAdded(self, change):
-        pass
-
-    def slaveConnected(self, slaveName):
-        pass
-
-    def slaveDisconnected(self, slaveName):
-        pass
-
     def notify_for_finished(self, build):
         results = build.getResults()
 
@@ -593,6 +583,8 @@ def handleAction(self, data, user):
         reactor.callLater(timeout, self.act, response)
 
 class IRCContact(Contact):
+    implements(IStatusReceiver)
+
     # this is the IRC-specific subclass of Contact
 
     def __init__(self, channel, dest):
@@ -860,6 +852,7 @@ def clientConnectionFailed(self, connector, reason):
 
 
 class IRC(base.StatusReceiverMultiService):
+    implements(IStatusReceiver)
     """I am an IRC bot which can be queried for status information. I
     connect to a single IRC server and am known by a single nickname on that
     server, however I can join multiple channels."""

docs/developer.texinfo

@@ -58,7 +58,9 @@ notifications.
 
 @item IStatusReceiver implementations
 
-Objects from the 'status' configuration key are attached directly to the buildmaster.
+Objects from the 'status' configuration key are attached directly to the
+buildmaster. These classes should inherit from StatusReceiver or
+StatusReceiverMultiService and include an 'implements(IStatusReceiver)' stanza.
 
 @end itemize